Outbreak of linezolid-resistant Staphylococcus haemolyticus in an Italian intensive care unit

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Linezolid is a critical antibiotic for treating infections caused by Gram-positive bacteria, including resistant strains.
• The emergence of linezolid resistance poses a significant threat to its clinical efficacy.
• Coagulase-negative staphylococci are common causes of hospital-acquired infections.

Observation:

• An outbreak of linezolid-resistant Staphylococcus haemolyticus strains was detected in an Intensive Care Unit.
• The resistant strains exhibited a high minimum inhibitory concentration (MIC) of 32 mg/L.
• Pulsed field gel electrophoresis confirmed that the strains were clonally related.

Findings:

• All identified Staphylococcus haemolyticus strains possessed the G2576T mutation, the genetic basis for linezolid resistance.
• The acquired linezolid resistance was stable, persisting even after multiple subcultures in the absence of the antibiotic.
• The resistance mechanism appears to be intrinsic and stable within the bacterial population.

Implications:

• The findings underscore the increasing challenge of multifocal emergence of linezolid resistance in healthcare settings.
• Stricter antimicrobial stewardship programs are necessary to control linezolid usage and preserve its effectiveness.
• Continued monitoring and research are crucial to combat the spread of antibiotic resistance and ensure patient safety.